1. Field of the Invention
The present invention relates to a laser working apparatus, a laser working method, a method for producing an ink jet recording head utilizing such laser working apparatus or method, and an ink jet recording head produced by such producing method, and more particularly to a laser working apparatus and a laser working method capable of ablation working of a work article and of fine working of a complex material and a complex structure such as of a micromachine, an IC and a hybrid IC device.
2. Related Background Art
In case of forming a fine structure directly on a work article by laser light, there is generally employed a harmonic wave of an excimer laser or a YAG laser, but, since the energy density of the laser light in the oscillated pulse is limited to the order of 100 megawatts at maximum, the laser working is difficult in materials of high thermal conductivity such as metals, ceramics or minerals (such as silicon) or those of low light absorbance such as quartz or glass, and can only be applied for the sublimation ablation working principally of organic resinous materials. Because of such drawbacks, in case of fine working of a compound material including or composed of the aforementioned metals, ceramics, minerals or glass, the desired structure can only be formed by a lithographic process requiring steps of resist coating, resist patterning by exposure, resist development, etching utilizing the resist pattern and resist ashing for each of the different materials.
Also in the manufacture of an ink jet recording head which is generally provided, in the ink discharge mechanism, with an ink discharge orifice for discharging ink, a liquid chamber containing ink to be supplied to the ink discharge orifice, an ink flow path connecting the ink discharge orifice and the liquid chamber, an energy generating element provided in a part of the ink flow path for generating energy for ink discharge and an ink supply aperture for ink supply to the liquid chamber from the exterior, it is being tried to form the ink discharge orifice in a compound material including a laminated metal film in order to provide the plate bearing the ink discharge orifice (hereinafter called orifice plate) with a function not achievable with a resinous material only. In such case there is applied press working process or lithographic pattern etching process, but the press working is limited in the precision and is unsuitable for fine working. Also the etching process is disadvantageous in cost because of the complex working process, and also in the significant investment required for the production facility, in consideration of the process tact time.
As explained in the foregoing, there is generally required a complex working process such as the lithographic process, in order to form a fine structure in the work article.
Therefore, the present applicant already proposed, for example in the Japanese Patent Applications Nos. 2000-187464, 2000-188333 and 2000-187146, means utilizing so-called femtosecond laser described for example in the xe2x80x9cNext Generation Optotechnology Reviewxe2x80x9d (published 1992 by Optronics Co.; Part 1 Elementary Technology; Generation and compression of ultra short light pulse, pp.24-31) and executing irradiation with the laser light in plural pulses of a high energy density in space and in time, emitted from a laser oscillator having a pulse emission time not exceeding 1 picosecond, in concentrated manner with a predetermined energy density, thereby achieving sublimation ablation working before the laser light is diffused as thermal energy in the work article. With such means, since the energy density in time is drastically increased (a pulse emission time not exceeding 150 femtoseconds and an optical energy exceeding 500 microjoules per pulse being achievable in the commercially available femtosecond lasers, thus providing an energy density of about 3 gigawatts in the oscillated pulse of the emitted laser light), and since the laser irradiation time is very short, the sublimation ablation working process can be completed before the laser light is diffused as thermal energy in the work article. Such phenomenon may be scientifically interpreted that the optical energy is not converted into thermal energy but directly functions as the lattice cleaving energy because the photons require a time of about 1 picosecond for conversion into phonons or thermal quantum particles by absorption in the electrons.
Such phenomenon allows to concentrate energy even in materials of high thermal conductivity such as metals, ceramics or minerals (for example silicon) thereby easily achieving the working by a multi-photon absorbing process, and the working becomes possible even in materials of low light absorbance such as glass, quartz or optical crystals as long as they have an absorbance of 0.1 to 1%, since, even in such materials, the optical energy density reaches a gigawatt level which is more than 100 times higher than that achievable with the excimer laser.
Consequently the optical ablation working, utilizing the high output femtosecond laser capable of emitting a high power laser light with a pulse emission time not exceeding 1 picosecond, is highly promising as the fine working process not limited in the material, and is therefore actively developed in recent years.
However, the above-mentioned laser oscillation system, capable of emitting the laser light with a pulse emission time not exceeding 1 picosecond, generally employs vertical mode synchronization for oscillation, and the compression of the laser pulse in time is realized by the vertical mode synchronization, which requires adjustment of an optical member in the laser system in the order of a micrometer. For this reason, the system is very sensitive to the thermal expansion or contraction of the members constituting the system, and, if the repeated oscillation state of the laser is changed for example by a burst oscillation or a modulation of the repeated oscillation frequency, the thermal equilibrium in the laser oscillator is perturbed to cause instability of the temperature therein, whereby the support member for the optical members causes thermal expansion or contraction to disrupt the optical adjustment of the micrometer order, thereby resulting in a variation in the oscillated pulse duration and the output energy of the laser light. In order to avoid such drawbacks, the above-mentioned laser oscillation system is operated under temperature control of the order of 0.1xc2x0 C. for the portions of laser oscillation and amplification, but such temperature control is still insufficient and it is still desirable to operate the system in a continuous pulse oscillation mode in a stationary state.
On the other hand, in case of using such continuous pulse oscillation mode for actual working process, a light intercepting device or a light intensity attenuating device has to be provided in the optical path of the continuously emitted laser light, but such device, if simply provided in the laser oscillator, results in the following drawbacks.
As explained in the foregoing, since the laser emission of the extremely short pulse emission time is achieved by the vertical mode synchronization, the optical members in the laser oscillation system have to be positioned with a precision of the order of a micrometer, and the entire laser oscillator is precisely controlled in temperature with a precision of the order of 0.1xc2x0 C. If a light intercepting device or a light intensity attenuating device is simply provided in the main body of such laser oscillator, such device absorbs or emits the energy of the laser, whereby the temperature in the laser oscillator is elevated by the absorption of the optical energy and the laser oscillation itself becomes extremely unstable.
Also, for achieving optimum fine working with a higher precision, it is not sufficient to merely consider the influence on the temperature control of the entire laser oscillating portion, in providing the light intercepting device or the like therein. For achieving optimum fine working with a higher precision by the optical ablation working, the burst irradiation of the laser light in continuous pulses of a constant frequency is not sufficient but it is also required to vary the repeating frequency of the laser light pulses or to vary the ratio in time of the laser irradiating state and the laser non-irradiating state, according to the physical characteristics of the work article, the structure to be formed or the proceeding of working. More specifically it is required to optimize the interval of laser irradiations or to avoid the change in the ablating characteristics resulting from the shielding and absorption of the light by the plasma cloud, according to the scattered state of the plasma, atomic and molecular particles generated by the optical ablation. However, if the oscillation frequency of the laser light pulses from the laser oscillation system constituting the light source is directly modulated, there results the aforementioned drawback that the thermal equilibrium is perturbed to alter the characteristics of the laser light.
In consideration of the foregoing, the object of the present invention is to provide a laser working apparatus and a laser working method capable of controlling the irradiation with the laser light continuously emitted from the laser oscillator without affecting the temperature control of the entire laser oscillating portion, thereby achieving desired optical ablation working, also a producing method for an ink jet recording head utilizing such laser working apparatus or method, and an ink jet recording head obtained by such producing method.
The above-mentioned object can be attained, according to the present invention, by a laser working apparatus, a laser working method, a producing method for an ink jet recording head utilizing such laser working apparatus or method, and an ink jet recording head obtained by such producing method, featured by the following configurations (1) to (30):
(1) A laser working apparatus for effecting optical ablation working by irradiating a work article with laser light from a laser oscillator capable of continuous emission of a light pulse of a large energy density in space and in time, with a pulse emission time not exceeding 1 picosecond;
wherein control means for controlling the irradiation of the laser light is provided in a position not affecting the temperature control of the laser oscillating portion and a configuration is provided for controlling the irradiation of the laser light continuously emitted from the laser oscillator by the control means thereby effecting optical ablation working on the work article.
(2) A laser working apparatus according to (1), wherein the control means is provided outside the laser oscillator or in a chamber separate from a laser oscillation chamber in the laser oscillator.
(3) A laser working apparatus according to (1) or (2), wherein the control means is a light intercepting device capable of transmitting or intercepting the laser light, and a configuration is provided for irradiating the work article with a predetermined number of pulses by the light intercepting device thereby achieving optical ablation working.
(4) A laser working apparatus according to (3), wherein the light intercepting device is arranged by a mechanical electromagnetic chopper.
(5) A laser working apparatus according to (3), wherein the light intercepting device is arranged by an electrical liquid crystal shutter.
(6) A laser working apparatus according to (3), wherein the light intercepting device achieves interception of light by a diffraction effect in an acoustooptical modulator (AOM).
(7) A laser working apparatus according to (3), wherein the light intercepting device achieves interception of light by a diffraction effect in an electrooptical modulator (EOM).
(8) A laser working apparatus according to (1), wherein the control means is light intensity attenuating means capable of controlling the attenuation of the intensity of the laser light, and a configuration is provided for irradiating the work article with a predetermined energy density by the light intensity attenuating means.
(9) A laser working apparatus according to (8), wherein the light intensity attenuating means is arranged by a variable light attenuator for controlling the intensity of the transmitting light by varying the incident angle of light.
(10) A laser working apparatus according to (8), wherein the light intensity attenuating means is arranged by a light absorbing filter.
(11) A laser working apparatus according to (1) or (2), wherein the control means is a light interception control device capable of repeating the transmission and interception of the transmitting light with a frequency smaller (or a period longer) than that of the consecutive light pulses emitted from the laser oscillator, and a configuration is provided for irradiating the work article with the consecutive light pulses at a predetermined interval by the light interception control device, thereby achieving optical ablation working.
(12) A laser working apparatus according to (11), wherein the light interception control device is arranged by a mechanical rotary chopper.
(13) A laser working apparatus according to (12), wherein the time ratio of transmission and interception of the light by the mechanical rotary chopper is set by the shape of a shielding plate of the mechanical rotary chopper.
(14) A laser working apparatus according to (11), wherein the light interception control device is arranged by an electromagnetically controlled mechanical shutter.
(15) A laser working apparatus according to (11), wherein the light interception control device is arranged by an electrical liquid crystal shutter.
(16) A laser working apparatus according to (11), wherein the light interception control device executes interception of the light utilizing the diffraction effect of an acoustooptical modulator (AOM).
(17) A laser working apparatus according to (11), wherein the light interception control device executes interception of the light utilizing the diffraction effect of an electrooptical modulator (EOM).
(18) A laser working apparatus according to (11), wherein the temperature increase of the light interception control device by the absorption of the laser light is prevented by air cooling means such as an air blower or by liquid cooling means such as a circulating liquid heat exchanger.
(19) A laser working apparatus according to (11), wherein the laser light reflected by the light interception control device is absorbed by a light absorbing material such as a carbon block.
(20) A laser working apparatus according to (11), wherein the repeating period of transmission and interception of the light by the light interception control device is controlled by the electrical or mechanical control of the light interception control device by controller means.
(21) A laser working apparatus according to (20), wherein the controller means is adapted to variably control the repeating period of transmission and interception of the light of the light interception control device, according to the physical properties of the work article and the shape thereof to be worked, or according to the state of progress of the working.
(22) A laser working apparatus according to (20), wherein the controller means is adapted to variably control the time ratio of transmission and interception of the light of the light interception control device, according to the physical properties of the work article and the shape thereof to be worked, or according to the state of progress of the working.
(23) A laser working apparatus according to (1), wherein the laser oscillator is provided with a spatial compression device for light propagation.
(24) A laser working apparatus according to (23), wherein the spatial compression device for light propagation is arranged by chirping pulse generation means and vertical mode synchronization means utilizing the optical wavelength dispersion characteristics.
(25) A laser working method for effecting optical ablation working by irradiating a work article with laser light from a laser oscillator capable of continuous emission of light pulses of a large energy density in space and in time, with a pulse emission time not exceeding 1 picosecond;
wherein the temperature of an area including the laser oscillator is controlled, and control means is provided, outside the temperature control area, on the optical axis of the laser light for controlling the irradiation of the laser light continuously emitted from the laser oscillator thereby effecting optical ablation working on the work article.
(26) A laser working method according to (25), wherein the control means is arranged by a light intercepting device capable of transmitting or intercepting the laser light, and the light intercepting device irradiates the work article with a predetermined number of pulses thereby achieving optical ablation working.
(27) A laser working method according to (25), wherein the control means is arranged by light intensity attenuating means capable of controlling the attenuation of the intensity of the laser light, and the light intensity attenuating means irradiates the work article with a predetermined energy density thereby achieving optical ablation working.
(28) A laser working method according to (25), wherein the control means is arranged by a light interception control device capable of repeating the transmission and interception of the transmitting light with a frequency smaller (or a period longer) than that of the consecutive light pulses emitted from the laser oscillator, and the light interception control device irradiates the work article with the consecutive light pulses at a predetermined interval, thereby achieving optical ablation working.
(29) A method for producing an ink jet recording head provided with an ink discharge orifice for discharging an ink droplet to be deposited on a recording medium, a liquid chamber for storing ink to be supplied to the discharge orifice, an ink flow path connecting the discharge orifice and the liquid chamber, an energy generating element provided in a part of the ink flow path and adapted to generate energy for discharging ink, an ink supply aperture for supplying the liquid chamber with the ink from the exterior etc., by working a member constituting at least a part of the ink flow path by a laser working apparatus;
wherein a member constituting at least a part of the ink flow path is sublimatedly worked by using the laser working apparatus according to either one of (1) to (24) or the laser working method according to either one of (25) to (28).
(30) An ink jet recording head provided with an ink discharge orifice for discharging an ink droplet to be deposited on a recording medium, a liquid chamber for storing ink to be supplied to the discharge orifice, an ink flow path connecting the discharge orifice and the liquid chamber, an energy generating element provided in a part of the ink flow path and adapted to generate energy for discharging ink, an ink supply aperture for supplying the liquid chamber with the ink from the exterior etc., in which a member constituting at least a part of the ink flow path is formed by a laser working apparatus;
wherein the ink jet recording head is produced by the producing method according to (29).
The present invention provides a laser working apparatus and a laser working method capable of achieving desired optical ablation working by controlling the irradiation of the laser light continuously emitted from the laser oscillator, without affecting the temperature control of the entire laser oscillating portion, and a method for producing an ink jet recording head utilizing such laser working apparatus or method and an ink jet recording head produced by such producing method.
Also the present invention provides a laser working apparatus and a laser working method capable of achieving precise laser working of predetermined depth and shape by irradiating the work article with a predetermined number of pulses by controlling the transmission and interception of the laser light, under stable laser oscillation and without affecting the temperature control of the entire laser oscillating portion, and a method for producing an ink jet recording head utilizing such laser working apparatus or method and an ink jet recording head produced by such producing method.
Also the present invention provides a laser working apparatus and a laser working method capable of achieving precise laser working with a smooth worked surface by irradiating the work article with a predetermined energy density by controlling the intensity of the laser light, under stable laser oscillation and without affecting the temperature control of the entire laser oscillating portion, and a method for producing an ink jet recording head utilizing such laser working apparatus or method and an ink jet recording head produced by such producing method.
Also the present invention provides a laser working apparatus and a laser working method capable of optimizing the interval of laser irradiation in consideration of the scattered state of the plasma and gaseous atoms or molecules generated by the optical ablation and avoiding the variation in the ablating characteristics resulting from the light interception and absorption by the plasma cloud, thereby achieving optimum laser working of high precision by controlling the repeating period of the laser light pulses or the time ratio of laser irradiating state and laser non-irradiating state according to the physical properties and work shape of the work article or the state of progress of working, without affecting the temperature control of the entire laser oscillating portion, and a method for producing an ink jet recording head utilizing such laser working apparatus or method and an ink jet recording head produced by such producing method.